diff --git a/dom/interfaces/xul/nsIDOMXULMultSelectCntrlEl.idl b/dom/interfaces/xul/nsIDOMXULMultSelectCntrlEl.idl
index 98c7f61fa370..03db9c3bc8f2 100644
--- a/dom/interfaces/xul/nsIDOMXULMultSelectCntrlEl.idl
+++ b/dom/interfaces/xul/nsIDOMXULMultSelectCntrlEl.idl
@@ -26,7 +26,6 @@ interface nsIDOMXULMultiSelectControlElement : nsIDOMXULSelectControlElement
   void selectItemRange(in nsIDOMXULSelectControlItemElement startItem, in nsIDOMXULSelectControlItemElement item);
 
   void selectAll();
-  void invertSelection();
   void clearSelection();
 
   // XXX - temporary, pending implementation of scriptable,
diff --git a/layout/xul/tree/nsITreeSelection.idl b/layout/xul/tree/nsITreeSelection.idl
index adb79a5131cd..d265b639ee96 100644
--- a/layout/xul/tree/nsITreeSelection.idl
+++ b/layout/xul/tree/nsITreeSelection.idl
@@ -63,11 +63,6 @@ interface nsITreeSelection : nsISupports
    */
   void clearSelection();
 
-  /**
-   * Inverts the selection.
-   */
-  void invertSelection();
-
   /**
    * Selects all rows.
    */
diff --git a/layout/xul/tree/nsTreeSelection.cpp b/layout/xul/tree/nsTreeSelection.cpp
index 73e848c704c7..5430df7f5f10 100644
--- a/layout/xul/tree/nsTreeSelection.cpp
+++ b/layout/xul/tree/nsTreeSelection.cpp
@@ -458,10 +458,6 @@ NS_IMETHODIMP nsTreeSelection::ClearSelection() {
   return NS_OK;
 }
 
-NS_IMETHODIMP nsTreeSelection::InvertSelection() {
-  return NS_ERROR_NOT_IMPLEMENTED;
-}
-
 NS_IMETHODIMP nsTreeSelection::SelectAll() {
   if (!mTree) return NS_OK;
 
diff --git a/toolkit/content/tests/chrome/test_hiddenitems.xul b/toolkit/content/tests/chrome/test_hiddenitems.xul
index b9a90fea57ab..79f06c8890b6 100644
--- a/toolkit/content/tests/chrome/test_hiddenitems.xul
+++ b/toolkit/content/tests/chrome/test_hiddenitems.xul
@@ -51,8 +51,6 @@ function testListbox(id)
   is(listbox.selectedItem.id, id + "_item2", id + ": Up didn't skip hidden item");
   listbox.selectAll();
   is(listbox.selectedItems.length, 7, id + ": Should have still selected all items");
-  listbox.invertSelection();
-  is(listbox.selectedItems.length, 0, id + ": Should have unselected all items");
   listbox.selectedIndex = 2;
   ok(listbox.selectedItem == listbox.getItemAtIndex(2), id + ": Should have selected the hidden item");
   listbox.selectedIndex = 0;
diff --git a/toolkit/content/tests/widgets/tree_shared.js b/toolkit/content/tests/widgets/tree_shared.js
index 1ddd622a1fef..474b9d30f15e 100644
--- a/toolkit/content/tests/widgets/tree_shared.js
+++ b/toolkit/content/tests/widgets/tree_shared.js
@@ -451,9 +451,6 @@ function testtag_tree_TreeSelection(tree, testid, multiple) {
     []
   );
 
-  // XXXndeakin invertSelection isn't implemented
-  //  selection.invertSelection();
-
   is(selection.shiftSelectPivot, -1, testid + "shiftSelectPivot set to -1");
 
   // rangedSelect and clearRange set the currentIndex to the endIndex. The
diff --git a/toolkit/content/widgets/richlistbox.js b/toolkit/content/widgets/richlistbox.js
index 994a58521948..ab4debc7d240 100644
--- a/toolkit/content/widgets/richlistbox.js
+++ b/toolkit/content/widgets/richlistbox.js
@@ -549,27 +549,6 @@
       this._fireOnSelect();
     }
 
-    // nsIDOMXULMultiSelectControlElement
-    invertSelection() {
-      this._selectionStart = null;
-
-      var suppress = this._suppressOnSelect;
-      this._suppressOnSelect = true;
-
-      var item = this.getItemAtIndex(0);
-      while (item) {
-        if (item.selected) {
-          this.removeItemFromSelection(item);
-        } else {
-          this.addItemToSelection(item);
-        }
-        item = this.getNextItem(item, 1);
-      }
-
-      this._suppressOnSelect = suppress;
-      this._fireOnSelect();
-    }
-
     // nsIDOMXULMultiSelectControlElement
     clearSelection() {
       if (this.selectedItems) {